The main objectives of this project are to develop very high frequency ultrasonic techniques (50 to 100 MHz) that use novel signal processing techniques to extract blood flow information from blood echoes for non-invasive assessment of blood velocity and vascular architecture, to apply these techniques to characterize subtle perfusion anomalies in ocular diseases (e.g, glaucoma and macular degeneration) and to monitor the effects of pharmacological and surgical procedures used to treat these conditions. The principal rationale behind the idea is that very high frequency ultrasound can be used to map very small blood vessels of diameter less than 20 fm with flow velocities as low as 0.2 mm/sec. Other approaches such laser Doppler flowmetry, fluorescein angiography and magnetic resonance imaging all have limitations. Currently these devices utilize PVDF transducers that have poor sensitivity. PVDF or PZT Annular arrays that allow better focusing, thus spatial resolution and sensitivity, are being developed to replace these single element transducers. These devices will be tested on animals and patients at University of Virginia and Cornell Medical College.